An ultrasound diagnostic system is now widely used to inspect the internal condition of a human body. The ultrasound diagnostic system may obtain an image of the single layer or blood flow of a soft tissue without using an invasive needle. This is typically performed through the process of radiating an ultrasound signal from the body surface of a target object to be diagnosed to a desired portion in the body, receiving the reflected ultrasound signal, and processing the received ultrasound signal (ultrasound echo signal). Compared to other medical imaging systems (e.g., X-ray diagnostic system, X-ray Computerized Tomography (CT) scanner, Magnetic Resonance Imaging (MRI) system, nuclear medicine diagnostic system, etc.), the ultrasound diagnostic system is relatively small in size and inexpensive. The ultrasound diagnostic system is further capable of displaying images in real-time and is highly safe from exposure to X-ray radiation or the like. Due to such advantages, the ultrasound diagnostic system is widely employed to diagnose the heart, abdomen and urinary organs, especially in the fields of obstetrics, gynecology and the like.
In a conventional ultrasound diagnostic system, transducers transmit ultrasound signals to a target object and receive signals reflected by the target object (echo signals). The echo signals show different patterns depending on whether the target object is stationary or moving. When the target object is moving toward the transducers, received signals have higher frequencies than when the target object is stationary. On the other hand, when the target object is moving away from the transducers, received signals have lower frequencies than when the target object is stationary. As such, the echo signals reflected by the moving target object are subject to the Doppler shift phenomenon. Due to the Doppler shift, the ultrasound diagnostic system can obtain velocity information that can be displayed on a display device. Further, the ultrasound diagnostic system can offer the velocity measurement of a blood flow based on the obtained velocity information.
Generally, contour tracing is required to detect the contour (sometimes referred to as a ‘trace line’) of a spectrum image. However, even when the spectrum image has aliasing, the conventional ultrasound diagnostic system does not consider the magnitude and direction of the aliasing when performing contour tracing. For this reason, the conventional ultrasound diagnostic system is disadvantageous since it cannot perform accurate contour tracing, as shown in FIG. 1. Therefore, the conventional ultrasound diagnostic system cannot provide accurate peak tracing.
Further, as the pulse wave (PW) gain for a spectrum image increases, the noise also tends to increase. Also, the noise varies for each spectrum image. However, when the conventional ultrasound diagnostic system performs the contour tracing on a spectrum image with increased noise, it determines a threshold for removing the noise based on the PW gain without analyzing the noise. Thus, since the noise varies depending on external environments (e.g., gel existence, probe type, etc.), the conventional ultrasound diagnostic system is disadvantageous in that it cannot perform accurate contour tracing, as shown in FIG. 2. Therefore, the conventional ultrasound diagnostic system cannot provide accurate peak tracing.